Organometallic compounds and uses thereof

ABSTRACT

WHERE M IS A GROUP IV TRANSITION METAL R1-5 ARE SUBSTITUENTS WHICH MAY BE THE SAME OR DIFFERENT N IS AN INTEGER FROM 0 TO 3, PROVIDED THAT WHEN M=TITA NIUM AND N=0,R1-5 ARE NOT ALL HYDROGEN, L IS AN ANIONIC LIGAND L&#39;&#39; IS A NEUTRAL LIGAND AND M IS AN INTEGER FROM 0 TO 2. ALSO PROCESSES FOR THEIR PREPARATION, AND THEIR USE AS OLEFIN, ESPECIALLY ETHYLENE, POLYMERIZATION INITIATORS.   (L&#39;&#39;)M   ((2-R1,3-R2,4-R3,5-R4,6-R5-PHENYL)-CH2-)(4-N)-M (L)N   ORGANOMETALLIC COMPOUNDS OF THE GENERAL FORMULA

United States Patent Office ABSTRACT OF THE DISCLOSURE 'Organometallic'compounds of the general formula M is a Group IV transition metal R aresubstituents which may be the same or different n is an integer from 0.to 3, provided that when M=titanium and n=0, R are not all hydrogen, Lis an anionic ligand L'is a neutral ligand and m is an integer from O to2.

where Also'processes for their preparation, and their use as olefin,especially ethylene, polymerization initiators.

This application is a division of Ser. No. 41,074, filed May 27, 1970,now US. Pat. 3,681,317.

This invention; relates to organometallic compounds, to processes fortheir preparation, and to their use as initiators for the polymerizationof unsaturated monomers.

The invention provides organo-metallic compounds of the general formula7 where M is a Group IV transition metal R are substituents which may bethe same or different,

n is an integer from to 3, provided that when M=tita nium and n=0, R arenot all hydrogen,

L is an anionic ligand L' is a neutral ligand and m is an integerfrom 0to 2.

Organic groups according to the formula in brackets above will bereferred to as benzyl groups.

Ligands L and L may be absent, in which case valency and co-ordinationrequirements are satisfied by the beuzyl groups. Such compounds will bereferred to as isoleptic." Ligands L, which are neutral, may be present,giving the metal a co-ordination number of 5 or 6, rather than the usual4 when L is absent.

R are preferably selected from hydrogen, alkyl groups containing one tosix carbon atoms, cycloalkyl, halogen, oxyalkyl in which the alkyl groupcontains from one to six carbon atoms, but other organic groups are alsosuitable, including longer chain alkyl and oxyalkyl, alkaryl, aryl,aralkyl and aryloxy groups. Further, one or more'pairs of gi-oups Rmaybe linked to form cyclic st'ruc't'ureses'pecially where two adjacentgroups form a 3,313,423 Patented May 28, 1974 second aromatic ring whichis coplanar with the ring already present. Examples of this type ofcompound are tetrakis(naphthylmethyl) compounds of the Group IV metals.

Ligands L are preferably halogen, but they may provide oxygen-metalbonds in the form of oxyhydrocarbyl or oxy-silicon groups.

Ligands L are suitably Lewis bases free from active hydrogen which wouldreact with the organo-metallic compound. Examples are tertiary phosphineoxides and amines such as tri(n-butyl)phosphine oxide and pyridine.

Isoleptic benzyl compounds according to our invention may be prepared bythe reaction of a tetrahalide of a Group IV transition metal with anorganometallic compound of a Group I to I11 metal which contains atleast one ligand of the general formula:

where R have the meaning ascribed above. Particularly convenient arebenzyl and substituted benzyl Grignard reagents. The reaction of theorganometallic compound and the transition metal halide are convenientlycarried out in liquid media, the second mentioned component being addedas a solution or suspension. Low temperature 0 C.) are preferred anddry, oxygen-free conditions are essential. Ether, or hydrocarbonsolvents are suitable. The product may be recovered by crystallizationafter removal of solvent in vacuo, or by addition of a precipitatingsolvent. The products are often soluble in aromatic solvents and it isconvenient to prepare, store and use the compounds of our invention insuch solvents. The precise selection of solvents varies with the benzylcompound being prepared. Procedures which may be used to free theproduct from magnesium and halogen are described later. The compoundsmust be stored in dry, oxygen-free conditions, but have reasonablethermal stability, compared with other transition metal organometalliccompound such as vr-allyl compounds. For example,tetrakis(benzyl)zirconium and hafnium may be kept at room temperaturefor 24 hours without serious decomposition, or at 0 C. for considerablylonger periods.

Compounds of our invention are characterized by the following NMR data.The methylene protons in the NMR spectrum usually show a single line inthe region 6.8-:- to 7.31- for titanium compounds and 8.07 to 8.61 forzirconium and hafnium compounds. The compounds are typically red(titanium) or yellow to orange-yellow (zirconium and hafnium).

Tetrakis(benzyl)zirconium can be isolated as orangeyellow crystals, M.P.113 C. (dec.), and tetrakis(benzyl) hafnium as yellow crystals M.P. 99C. (dec.).

Benzyl compounds in which ligands L are present, n being a positiveinteger from 1 to 3, may be prepared by the reaction of isolepticcompounds according to our invention with an acidic compound of the typeHX where X is an anionic group, such as halide, oxyhydrocarbyl oroxy-silicon.

The amounts of HX used depends on the number of ligands L required. Thusequimolar amounts of tetrakis (benzyDZirconium and hydrogen chloridereact to form tris(benzyl)zirconium monochloride, and two moles ofhydrogen chloride with one mole of the isoleptic zirconium compound givebis(benzyl) zirc onium dichloride, and so on.

The reaction is carried out by adding the required amount of acid HX toa solution of the benzyl compound. Hydrogen halides may be added bydistilling the gas into the benzyl solutionat'low temperature, e.g.about C.

Further, one or two ligands L' may be introduced into the compoundsdescribed whether L is present or not by direct reaction, preferably insolution. For example, to a solution of tetrakis(benzyl)zirconium one ortwo molar equivalents of pyridine may be added and the appropriate 5 or6 co-ordinate complex may be isolated.

According to a further aspect of our invention, benzyl compounds of thetype described above may be used to initiate the polymerization orcopolymerization of olefinically unsaturated monomers. The processrequires that the Group IV transition metal compound is contacted withthe olefin under substantially dry and oxygen-free conditions.

Particularly useful initiators are the benzyl compounds of zirconium andhafnium according to formula (1) where m= and R =H. These areconsiderably more active initiators for the polymerization of ethylenethan in the corresponding titanium compound. Also useful are compoundsaccording to formula 1) in which preferably 1, or at most 2 of thegroups R are substituents other than hydrogen, and also m=O.

Olefinically unsaturated monomers which may be polymerized by ourprocess include olefins, such as ethylene or propylene; diolefins, suchas butadiene; and polar monomers, such as styrene and methylmethacrylate. Mixtures of such monomers may also be copolymerized; butany given monomer may not necessarily be copolymerizable with all othermonomers of the group.

The polymerization process is elfected by contacting the monomer ormonomers with one or more of the compounds described, under oxygenandmoisture-free conditions. The monomer may be used as a liquid or, if itis not liquid under the reaction conditions, in solution in a suitablesolvent. Solvents which may be used include aliphatic or aromaticsolvents such as pentane, hexane, toluene or mixtures of such solvents.The initiators, being solids, are preferably added to the reactor assolutions in a solvent of the types mentioned above.

Pressures of one atmosphere and above are preferred; but the choice ofpressure will be largely dependent on the monomer being polymerized. Forexample, when polymerizing ethylene, pressures of about kg./cm. or aboveare preferred and much higher pressures, for example up to 3000 kg./cm.may be used. The use of the last mentioned very high pressures enablesnormal high pressure reactor technology to be used, including workingunder conditions in which the monomers, polymer and initiator co-existas a single fluid phase.

The initiators may be used over a wide temperature range, e.g. from 0 C.to 200 C., final choice of temperature being dependent upon the natureof the benzyl compound and the monomer being polymerized. When ethyleneis being polymerized it is often preferred to work near the upper end ofthe range, for example from 130 C. to 160 C. This is especially so whenworking under the aforementioned single fluid phase conditions.

Although the substituted benzyls of our invention may be readilyisolated from solution, it will be appreciated that they may be used toinitiate polymerization without isolation, for example, by utilizing theentire reaction medium, preferably after filtering to removeprecipitated magnesium chloride if the compound has been prepared by theGrignard route.

The concentration of initiator in the polymerization reaction mixture isnot critical and is ideally kept as low as is possible consistent withobtaining a reasonable activity. However, it generally lies between 0.05and 10 mmoles/ litre. I

The invention will be illustrated by the following examples.

GENERAL PROCEDURE '(a) Preparation of Grignard reagent moles of theappropriately substituted benzyl chloride, dissolved in 300 m1. ofether, are added with stirring 4 e to a suspension of 60 g. of magnesiumturnings in 400 ml. of ether over a period of two hours, the reactionbeing initiated by the addition of a crystal of iodine. The yield ofGrignard reagent is estimated by the normal titration technique. Using232 ml. of benzyl chloride C H CH Cl, the yield was about 92%. Y i

(b) Preparation of transition'metal benzyl compound, A group IVtransition metal tetrahalide is added to an etheral solution of theappropriately substituted benzyl magnesium chloride prepared asunder (a)above, thetemperature of which is maintained at about -'20 Afteraddition of all the metal halide, the solution lS stirred for two hoursat ,-20 C. andthen for a further '(2) an oil, in which case therequisite quantity of dioxan is added to precipitate all magnesiumchloride from solution, which is then filtered, concentrated and setaside to crystallize at 25 C. When the crystals form they are againseparated from the mother liquors and taken up in an aromatic solvent.It is noted that, although the crystals may be separated and stored inthe solid state, it is preferred to store them in aromatic solution, asit is in such media that the compounds are commonly used. This pro-'cedure is particularly useful for preparing tetrakis- (benzyl)zirconiumand halfnium.

For complexes soluble in aliphatic solvents-The ethereal solutioncontaining the transition metal benzyl compound plus small amounts ofdissolved magnesium chloride is treated to remove the ether underreduced pressure at l5 C. and the resulting solid product stirred withpentane at room temperature. Filtration of the resulting extract yieldsa solution of the benzyl compound in pentane.

EXAMPLE i Using the procedure given under. (b) above, 30 g. of zirconiumtetrachloride was reacted with benzyl magnesium chloride. Thebrown/yellow solution produced contained 33.6 g. of zirconiumtetrabenzyl. (Yield 59%).

Crystals of zirconium tetrabenzyl isolated from this solution had amelting point of 113 C. with decomposition. A solution of the product indeuterobenzene was analysed by NMR and showed peaks at about 3.601 and f2.901, assignable to aromatic protons, and apeakat 8.41, assignable tomethylene protons.

Crystallographic examination of afsingle crystal of the productindicated a tetrahedral arrangement of four ben zyl groups about asingle zirconium atom.

EXAMPLE 2 Using the procedure given under (b) above, 32 g. (0.1

mole) of hafnium tetrachloride was reacted with 0.4 mole of benzylmagnesium chloride in ether. The resultant yellow solution was filteredand then evaporated tojdryness under vacuum at room temperature. Theyellow solid residue was dissolved in the minimum quantity of toluepe'at room temperature and the resultant solution filtered and cooled to-60 C. Yellow crystals (21 g.) separated from the solution and werefurther lization from toluene.

The product hafnium tetrabenzyl, which mutate kept for long periods atroom temperature under nitrogenwith out visible deterioration, had an m.pt. of C. with decomposition. Its NMR spectrum was verysiniilaftoappropriate pnriiiedb'y recrystal' that reported above for zirconiumtetrabenzyl, having multiplets at 3.51 and 3.01- and a singlet at 8.551.

EXAMPLES 3 AND 4 A 1 litre stainless steel stirred autoclave was purgedsix times with high purity ethylene to remove traces of oxygen andmoisture. 400 ml. of toluene was then introduced by syringe under acountercurrent of ethylene and the system pressurized with kg./cm. ofhydrogen and 27 kgjcm." of ethylene to ensure saturation of the solvent.1.5 millimoles of initiator in toluene solution was then injected bysyringe and the reactor re-pressurized. The temperature of .theautoclave was raised to 160 C. and polymerization allowed to continuefor 1 hour. At the end of this time the polymer was removed, washed withacid methanol and dried. The polymer was weighed and the yieldcalculated in terms of g. of polyethylene per millimole of initiator perkg./cm. per hour. The results are set out in Table 1. An equivalentresult using titanium tetrabenzyl is given by way of comparison.

Yield of polyethylene, g./mmole/ Example Initiator kg. emr lhr.

3 Zr(benzyl)4. 0.75 4 Hi(benzyl) 0.42 Ti(benzyl)4 0. 19

EXAMPLE 5 Polymerization of p-bromo styrene with Zr or Hf tetrabenzyl.

' Zirconium tetrabenzyl (0.154 g. in 13 ml. toluene) was added to 47.6g. of p-bromo styrene under nitrogen. The resultant mixture was dilutedto 100 ml. with toluene and maintained at 30 C. for 24 hours. At the endof this time the polymer produced was precipitated by the addition ofmethanolic hydrochloric acid, removed from the solution by filtrationand dried. Yield 4.8 g. poly(p-bromo styrene).

EXAMPLES 6 TO 12 Zirconium and titanium tetra(substituted benzyl)compounds were made using the appropriate form of the general procedure(b) above. The compounds were analyzed by NMR spectroscopy giving theresults shown in the fol lowing table.

12-.. 6.921 Ti --CH@) 1 4 6 EXAMPLES 13 TO 17 A 1 litre stainless steelstirred autoclave was purged six times with high purity ethylene toremove traces of oxygen. and moisture. 400 ml. of toluene was thenintroduced by syringe under a countercurrent of ethylene and the systempressurized with a 10 .kg. cm.- of hydrogen and 27 kg. cmr of ethyleneto ensure saturation of the solvent. 1.5 millimoles of initiator intoluene solution was then injected by syringe and the reactorre-pressurized. The temperature of the autoclave was raised to 160 C.and polymerization allowed to continue for 1 hour. At the end of thistime the polymer was removed, washed with acid methanol and dried. Thepolymer was weighed and the yield calculated in terms of g. ofpolyethylene per millimoles of initiation per kg./cm. per hour. Theresults are set out in the table below.

Yield of polyethylene, gJmmole/ Example Initiator kg. cmfl/hr.

13 0. 94 mean-@0113).

Zr(CH -OCHa)| Zr -CH2 0 16 0. 83 Ti(CH2- CHa)a Ti -CH2 Cl 4 It will beseen from the above results that substituents in the aromatic ring ofthe benzyl group afiect the polymerization ethylene activity of thecompounds, and the activities are all considerably higher than whenunsubstituted titanium benzyl is used.

EXAMPLES 18 TO 20 The procedure of Examples 13 to 17 was repeated usingdifierent initiators, prepared by the general procedure above. Gaspressures were: ethylene 10 kg. cmrhydro gen 10 kg. cmr Amounts ofinitiator: 1 millimole. Temperature: C. The results are shown in thetable below.

hydrogen chloride :575 g.) was distilled into the solution at 80 C. withstirring. A rapid reaction occurred and thecolor ot'the solution changedfromiyellow to orange. Analysis of the solution was consistent with theformation of tris(benzyl)zirconium chloride; (ZrzCl ratio=1:0.92,asmeasured). 1.2 millimoles of this compound was used as an ethylenepolymerization initiator under the conditions of Examples 13 to 17, butwith ethylene and hydrogen pressures both at 10 kg./cm.- After 1 hour at80 C., the polymer yield was 6.0 g. which gives an activity of 5.1g./rnlllimole /kg. cm.- /h'r.

EXAMPLE 22 The above procedure was repeated using half the amount oftetrakis(benzyl)zirconium. At -80 C. an orange solid and orange solutionwere produced. 0n warming to 0 C. the solid dissolved and was reformedas bright orange crystals at 30 C. Analysis of the crystals wasconsistent with the formation of bis(benzyl) zirconium dichloride (ZrzClratio=1:2.02 as measured). 1.0 millimoles of this compound was used asan ethylene polymerization initiator under the conditions of Examples 13to 17, but with ethylene and hydrogen pressures both at 10 kg. emf.After 1 hour at 80 C., the polymer yield was 45 g. which gives anactivity of 4.5 g./millimole/kg. cm.- /hr.

EXAMPLE 23 The procedure of Examples 13 to 17 was repeated usingtetrakis(benzyl)zirconium (5 millimoles) to polymerize propylene.

Pressure kg./crn.'- 16.5 Temperature C 120 Time hours 4 Yield g 0.2

EXAMPLES 24 AND 25 Preparation of derivatives containing neutral ligandsTo a stirred solution of tetrakis(benzyDzirconium (1 g.) in benzene (8ml.) maintained at 10 C. was added, dropwise, pyridine (0.177 g.)dissolved in a small quantity of benzene. The colour changed from yellowto orange. The NMR spectrum of the resulting solution showed thepresence of a new peak at 7.811 and absence of the usual tetra benzylpeak at 8.47. Analysis was consistent with tetrakis(benzyl)zirconiummonopyridine.

The above procedure was repeated using 0.354 g. of pyridine. The colourchanged from yellow to orange-red. The NMR spectrum showed a new peak at7.901- and the absence of a peak at 8.4T. In addition, a new double peakappeared at 1.777, assignable to the a protons of pyridine co-ordinatedto metal. Analysis was consistent with tetrakis(benzyl) zirconium bis(pyridine).

R R R R and R are selected from What'isclaimed is? f j f L.

1. An organometailic compoundofthe general formula:

V L I RI R4 where I g M is a group IV transition metal; I

the 'group 6onsisting of hydrogemalkyl, cycloa'lkyl, halogemoxyalkyl,

alkaryl, aryl, aralkyl, aryloxy and two adjacentR f groups joinedtogether to complete an aromatic ring,

n is an integer from 0 to 3, provided that when M=tita nium, R are notall hydrogen,

L is halogen;

L is pyridine; and

m is an integer from 0 to 2.

2. An organometallic compound according to claim 1 in which M isselected from zirconium and hafnium and eachRis hydrogen.

3. An organometallic compound according to claim 1 in which at least oneof R is a substituent as defined other than hydrogen. e e

4. An organometallic compound according to claim 3 in which R isselected from alkyl groups having from 1 to 6 carbon atoms, Halogen,andhxyalkyl'groups having from 1 to 6 carbon atoms.

5. An organometallic compound according to claim 1 selected from thegroup consisting of Y i tetrakis(benzyl)zirconium and tetrakis(benzyl)hafnium, tetrakis(p-methoxybe'nzyl)zirconium, I i tetrakis(p-methoxybenzyl titanium, tetrakis(at-naphthylmethyUtitanium, J Vtetrakis (a-naphthylrheth'yl)Zircniuin, a tetrakis(p-methylbenzyl)zirconium',- tetrakis(p-methy1 benzyl)titaniu-m,'tetrakis(o-chlorobenzy1 titanium; tetrakis(p-fiuorobenzyl)zirconium, Vtetrakis(p-chlorohenzyl)zirconium;-tetrakis(2,4,6-trimethylbenzyl)zirconium, tris(benzyl)zirconiumchloridea n'd 'bis(benzyl)zirconiumdichloride.

6. An organometallic compound according to claim i selected fromtetrakis(-benzyl)zirconium mono(pyridine) and tetrakis(benzyl)zirconiumbis(pyridine).-

I H References 7 I U Chemical Abstracts, vol. 67, 8.222% (1967.).Chemical Abstracts, vol. 69, 9.720021 (1968 HELEN M. s. SNEED;Primary.Eraminer, Y A

- s. or. XiR. 260429.5,270

